The use of a hand operated pointing device for use with a computer and its display has become almost universal. By far the most popular of the various devices is the conventional (mechanical) mouse, used in conjunction with a cooperating mouse pad. Centrally located within the bottom surface of the mouse is a hole through which a portion of the underside of a rubber-surfaced steel ball extends. The mouse pad is typically a closed cell foam rubber pad covered with a suitable fabric. Low friction pads on the bottom surface slide easily over the fabric, but the rubber ball does not skid, but instead rolls as the mouse is moved. Interior to the mouse are rollers, or wheels, that contact the ball at its equator and convert its rotation into electrical signals representing orthogonal components of mouse motion. These electrical signals are coupled to the computer, where software responds to the signals to change by a .DELTA.x and a .DELTA.y the displayed position of a pointer (cursor) in accordance with movement of the mouse. The user moves the mouse as necessary to get the displayed pointer into a desired location or position. Once the pointer on the screen points at an object or location of interest, one of one or more buttons on the mouse is activated with the fingers of the hand holding the mouse. The activation serves as an instruction to take some action, the nature of which is defined by the software in the computer.
Unfortunately, the usual sort of mouse described above is subject to a number of shortcomings. Among these are deterioration of the mouse ball or damage to its surface, deterioration or damage to the surface of the mouse pad, and degradation of the ease of rotation for the contact rollers (say, (a) owing to the accumulation of dirt or of lint, or (b) because of wear, or (c) both (a) and (b)). All of these things can contribute to erratic or total failure of the mouse to perform as needed.
The underlying reason for all this trouble is that the conventional mouse is largely mechanical in its construction and operation, and relies to a significant degree on a fairly delicate compromise about how mechanical forces are developed and transferred.
Over the years, a number of optical techniques have been proposed for a computer mouse, but to date the mechanical mouse remains the most widely used pointing device. One recent optical development that appears likely to gain a significant degree of acceptance is that described in U.S. patent application Ser. No. 09/052,046, entitled SEEING EYE MOUSE FOR A COMPUTER SYSTEM, filed Mar. 30, 1998, by Gordon, Knee, Badyal and Hartlove and assigned to Hewlett-Packard Co. That Application discloses the use of techniques described in the aforementioned incorporated Patents to produce an optical mouse that navigates upon an arbitrary surface. The device disclosed therein is a non-mechanical mouse that is viable from a manufacturing perspective, relatively inexpensive, reliable, and appears to the user as essentially the operational equivalent of the conventional mouse. This new type of optical mouse has a familiar "feel" and is free of unexpected behaviors. It does not rely upon cooperation with a mouse pad, whether special or otherwise, but is instead able to navigate upon almost any arbitrary surface. It uses a single imaging integrated circuit to track translation of that circuit (and by implication, the mouse itself) across the arbitrary surface.
Freely movable scanners are self contained appliances that are moved across a document surface. The simplest of these devices simply produce a strip of paper bearing a facsimile of the scanned material. More sophisticated devices create a raster representation in a memory and whose data may be transferred to a computer through a custom interface. That data might include several passes over a document (say, overlapping parallel left to right passes from top to bottom of page) whose associated raster images are subsequently assembled into a pixel by pixel representation of the entire document by stitching software within the computer. These classes of device all assume motion in one direction and scanning [either with charge coupled devices (CCD's) or contact image sensors (CIS's)] in a direction perpendicular to that motion. This is often enforced mechanically by a device-wide roller placed parallel to the image sensor, and whose purpose is to prevent a twisting or yawing motion of the device as it is moved across the document. Rotation of the roller indicates displacement, and is taken as a definition of the aforementioned motion in one direction.
A more sophisticated hand held scanner is disclosed by the incorporated Patents. A navigation mechanism is disposed at each end of an image sensor. The user is allowed to move the scanner over the document in any manner deemed suitable, even scanning the same material multiple times from the same or different directions. This becomes possible because the data produced from each scanning operation can now be processed to compensate for arbitrary scanner motion and permit finding a value for each element in the pixel grid associated with the final representation of the document or image. The hand held scanner disclosed by the incorporated Patents internally performs such processing, including the stitching of image segments together to produce a complete image. A small view screen on the scanner allows the user to see a low resolution approximation of the result, so that missed areas can be re-scanned before the scanner is removed from the document. A complete scanned image is transferred to a using environment, (e.g., a computer) at a later time through an appropriate interface.
Although the disclosed freely movable hand held scanner with two navigation sensors works quite well, it is nevertheless not ideally matched to certain environments. It is perhaps best suited for use in out-of-the-office settings where a stand alone scanner is the only scanner practical. Internally, that scanner has an impressive amount of processing power and memory, not to mention a large battery.
People often have computers at their desks, and many also have a use for a scanning capability. A conventional flat bed scanner takes up extra space, and a compact type that accepts a roller fed document cannot scan things that are not a separate individual sheet of paper. The high quality and error corrected result of the freely moveable hand held scanner is desirable, but the small viewing screen, significant price and bothersome data transfer operation are discouraging factors. It would be desirable if any document could be quickly scanned into the computer without undue fuss or expense, and without expending the desktop space needed by a flat bed scanner.